Gcn2 eIF2a kinase mediates combinatorial translational regulation through nucleotide motifs and uORFs in the mRNA 5’ leader regions
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PROVIDER: PRJNA599945 | ENA |
REPOSITORIES: ENA
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Project description:Cellular signaling controls translation through cis regulatory elements found in mRNAs. Gcn2 is the master regulator of translation during nutrient limitation in normal and cancer cells. Activated Gcn2 phosphorylates eIF2a, thereby repressing general translation while activating translation of specific mRNAs with upstream ORFs (uORFs) in its leader regions. Here we performed genome-wide measurement of mRNA translation during histidine starvation in fission yeast Schizosaccharomyces pombe. Polysomal microarray hybridization experiments identified a group of 1779 genes whose translation is up-regulated in Gcn2-dependent manner. We find that translation is reprogrammed to enhance organellar synthesis and transcription and repress ribosome synthesis. The 1779 genes included gcn5 and hri2 shown to promote growth under histidine starvation. They encode histone acetyl transferase and heme-binding eIF2a kinase activated by oxidative stress, and their 5’-leader contains 3 or 4 uORFs, respectively. Our reporter studies show that uORFs in gcn5 and hri2 operate similarly to those found in S. cerevisiae GCN4, the founding case for uORF-dependent regulation. Moreover, motif analysis identified 5’-UGA(C/G)GG-3’ as a motif promoting translation during starvation. Using hrd1 5’UTR with such a motif, we demonstrated its requirement in Gcn2-dependent translational control. To our knowledge, this is the first nucleotide motif found to be responsible for translational control by Gcn2. We propose that Gcn2 mediates translational control of more specific mRNAs than previously anticipated
2020-09-23 | GSE143299 | GEO
Project description:To study the mitochondrial stress response HRI-eIF2a-ATF4 signaling pathway in mitochondrial cardiomyopathy , we generated Ptpmt1 cardiomyocytes-specific Knockout mcie, Eif2a mutant mcie, Gcn2 Knockout mcie, and Hri Knockout mcie
2022-04-21 | GSE201042 | GEO
Project description:General translational repression is predicted as a key process to reduce energy consumption under hypoxia. We have previously showed that mRNA loading onto polysome is reduced in Arabidopsis under submergence. Here, we showed that plant stress activated GCN2 (general control nonderepressible 2) can phosphorylate eIF2a (Eukaryotic Initiation Factor 2a) in Arabidopsis under submergence, and this process is reversible after desubmergence. Compared to the wild-type, the reduction in polysome loading during submergence was less severe in the gcn2 mutant. Transgenic lines overexpressing GCN2 had more ATP and conferred better tolerance under submergence, suggesting that GCN2 might modulate the dynamics of translation to adjust the energy homeostasis under hypoxia. Interestingly, GCN2-eIF2a signaling was activated by ethylene under submergence. However, GCN2 activity was not affected in ein2-5 and eil1ein3 under submergence, suggesting that GCN2 activity was regulated by noncanonical ethylene signaling. In addition, the polysome loading was retained in both ein2-5 and etr1-1 under submergence, implying that ethylene modulated the dynamic translation under submergence via EIN2 and GCN2. Notably, our NGS analysis also demonstrated that EIN2 and GCN2 regulated the translation of 23 core hypoxia genes as well as 53% translational repressed genes under submergence. On the other hand, EIN2 and GCN2 also affected the expression of genes involved in hypoxic response, ethylene response, biotic stress and negative regulation of cytokinin signaling. Taken together, these demonstrated that entrapped ethylene triggers GCN2 and EIN2 to ensure the translation of stress required proteins under submergence and also provide a step stone for future investigation how eukaryotic cells modulate the translation to response for the changeable environments.
2022-06-08 | GSE149414 | GEO
Project description:The integrated stress response (ISR) is a central signalling network that enables eukaryotic cells to respond to a variety of different environmental stresses. Such stresses cause ribosome collisions that lead to activation of the kinase Gcn2, resulting in the phosphorylation and inactivation of eukaryotic initiation factor 2 and thereby promoting selective translation of mRNAs to restore homeostasis. Despite the importance of the ISR and intensive study over the past decades, structural insight into how Gcn2 interacts with ribosomal particles has been lacking. Using ex vivo affinity purification approaches, we have obtained a native structure of a Gcn2 dimer in complex with the ribosomal 60S subunit. The Gcn2 dimer is formed by dimerization of the histidine tRNA synthetase-like domains, which establish extensive interactions with the stalk-base and sarcin-ricin loop of the 60S subunit. The C-terminal domain of Gcn2 is also dimerized and occupies the A- and P-site tRNA binding sites at the peptidyl-transferase center of the 60S subunit. Complementary functional studies indicate that binding of Gcn2 to the 60S subunit does not require the co-activators Gcn1 or Gcn20, nor does it lead to phosphorylation of eIF2a. Rather, upon stress, we observe a shift of Gcn2 from the 60S subunit into the colliding ribosome fraction, suggesting that the Gcn2-60S complex represents an inactive stand-by state to enable a rapid redistribution to collided ribosomes, and thereby facilitating a quick and efficient response to stress.
2024-09-16 | PXD055898 | Pride
Project description:In eukaryotes, regulation of mRNA translation enables a fast, localized and finely tuned expression of gene products. Within the translation process, the first stage of translation initiation is most rigorously modulated by the actions of eukaryotic initiation factors (eIFs) and their associated proteins. These 11 eIFs catalyze the joining of the tRNA, mRNA and rRNA into a functional translation complex. Their activity is influenced by a wide variety of extra- and intracellular signals, ranging from global, such as hormone signaling and unfolded proteins, to specific, such as single amino acid imbalance and iron deficiency. Their action is correspondingly comprehensive, in increasing or decreasing recruitment and translation of most cellular mRNAs, and specialized, in targeting translation of mRNAs with regulatory features such as a 5’ terminal oligopyrimidine tract (TOP), upstream open reading frames (uORFs), or an internal ribosomal entry site (IRES). In mammals, two major pathways are linked to targeted mRNA translation. The target of rapamycin (TOR) kinase induces translation of TOP and perhaps other subsets of mRNAs, whereas a family of eIF2 kinases does so with mRNAs containing uORFs or an IRES. TOR targets translation of mRNAs that code for proteins involved in translation, an action compatible with its widely accepted role in regulating cellular growth. The four members of the eIF2 kinase family increase translation of mRNAs coding for stress response proteins such as transcription factors and chaperones. Though all four kinases act on one main substrate, eIF2, published literature demonstrates both common and unique effects by each kinase in response to its specific activating stress. This suggests that the activated eIF2 kinases regulate the translation of both a global and a specific set of mRNAs. Up to now, few studies have attempted to test such a hypothesis; none has been done in mammals. We use array analysis to determine the global mRNA shift into polysomes following a stress response, and to compare the translational response following activation of GCN2 versus PERK, two of the four eIF2alpha kinases. Experiment Overall Design: Gcn2 wild-type or knockout mouse liver were perfused with complete amino acids media or media lacking methionine for RNA extraction and hybridization of Affymetrix microarrays. RNA was extracted from unfractionated liver samples and polysome fraction of samples separated on sucrose density gradient. To minimize biological variations, we pooled RNA from two perfused liver samples to use in each array analysis. The conditions were total and polysome fraction of Gcn2+/+, +Met or -Met; total and polysome fraction of Gcn2-/-, +Met or -Met. Each array analysis was done in duplicate.
2009-11-23 | E-GEOD-11496 | biostudies-arrayexpress
Project description:We apply ribosome profiling here to assess the role of eIF2A in translation initiation. For this we test the change in translation efficiency between HeLa control and eIF2A-KO cells, however we do not find any transcript to depend on eIF2A. Since eIF2A is thought to take over the function of eIF2 when eIF2 is inhibited, we also test conditions where the integrated stress response is activated, thereby leading to eIF2 inactivation. In none of our assays, however, could we detect a role of eIF2A in translation initiation.
2024-11-29 | GSE282509 | GEO
Project description:Gene expression profile at Ptpmt1 cardiomyocytes-specific Knockout mcie, Eif2a mutant mice, Gcn2 Knockout mice, and Hri Knockout mice
| PRJNA828131 | ENA
Project description:Earlier investigations have associated mammalian eIF2A with Met-tRNAi binding to the 40S subunit and its recruitment to specialized mRNAs in a GTP-independent manner. Additionally, eIF2A has been implicated in non-AUG start codon initiation, particularly under conditions where eIF2 function is attenuated by phosphorylation of its α-subunit during stress or starvation. However, the precise role of eIF2A in vivo translation remains unclear. Moreover, it's uncertain if the conserved ortholog in budding yeast can functionally substitute for eIF2 during stress. To address these questions, we conducted ribosome profiling on a yeast deletion mutant lacking eIF2A, alongside isogenic wild-type (WT) cells, both in the presence or absence of eIF2α phosphorylation induced by amino acid starvation.
2024-01-03 | GSE241473 | GEO
Project description:Translation initiation is a complex and highly regulated process that represents an important mechanism, controlling gene expression. eIF2A was proposed as an alternative initiation factor, however, its role and biological targets remain to be discovered. To further gain insight into the function of eIF2A in Saccharomyces cerevisiae, we identified mRNAs associated with the eIF2A complex and showed that 24% of the most enriched mRNAs encode proteins related to cell wall biogenesis and maintenance. In agreement with this result, we showed that an eIF2A deletion sensitized cells to cell wall damage induced by calcofluor white. eIF2A overexpression led to a growth defect, correlated with decreased synthesis of several cell wall proteins. In contrast, no changes were observed in the transcriptome, suggesting that eIF2A controls the expression of cell wall-related proteins at a translational level. The biochemical characterization of the eIF2A complex revealed that it strongly interacts with the RNA binding protein, Ssd1, which is a negative translational regulator, controlling the expression of cell wall-related genes. Interestingly, eIF2A and Ssd1 bind several common mRNA targets and we found that the binding of eIF2A to some targets was mediated by Ssd1. Surprisingly, we further showed that eIF2A is physically and functionally associated with the exonuclease Xrn1 and other mRNA degradation factors, suggesting an additional level of regulation. Altogether, our results highlight new aspects of this complex and redundant fine-tuned regulation of proteins expression related to the cell wall, a structure required to maintain cell shape and rigidity, providing protection against harmful environmental stress.
2023-09-15 | PXD043985 | Pride
Project description:Residual cell-intrinsic innate immunity in cancer cells hampers infection with oncolytic viruses. Control of mRNA translation is an important feature of innate immunity, yet the identity of mRNA substrates that participate in host defences remain ill-defined. We characterized the translatome of resistant murine “4T1” breast cancer cells infected with three of the most clinically advanced oncolytic viruses: Herpes Simplex virus 1, Reovirus and Vaccinia virus. Common among all three infections were translationally de-repressed mRNAs including Inpp5e, encoding an inositol 5-phosphatase that modifies lipid second messenger signalling. We found that viral infection induced expression of an Inpp5e mRNA variant that lacks repressive upstream open reading frames (uORFs) within its 5’ leader and is efficiently translated. Furthermore, we show that INPP5E contributes to antiviral immunity by altering virus attachment. These findings uncover a role for translational control through alternative 5’ leader expression and assign an antiviral function to the ciliopathy gene INPP5E.
2019-11-30 | GSE137757 | GEO